Oral care products, such as dentifrice and mouthwash, are routinely used by consumers as part of their oral care hygiene regimens. It is well known that oral care products can provide both therapeutic and cosmetic hygiene benefits to consumers. Therapeutic benefits include caries prevention which is typically delivered through the use of various fluoride salts; gingivitis prevention, by the use of an antimicrobial agent such as stannous fluoride, triclosan, essential oils; or hypersensitivity control through the use of ingredients such as strontium chloride or potassium nitrate. Cosmetic benefits provided by oral care products include the control of plaque and calculus formation, removal and prevention of tooth stain, tooth whitening, breath freshening, and overall improvements in mouth feel impression, which can be broadly characterized as mouth feel aesthetics. Calculus and plaque along with behavioral and environmental factors lead to formation of dental stains, significantly affecting the aesthetic appearance of teeth. Behavioral and environmental factors that contribute to teeth staining propensity include regular use of coffee, tea, cola or tobacco products, and also the use of certain oral products containing ingredients that promote staining, such as cationic antimicrobials and metal salts.
Thus daily oral care at home requires products with multiple ingredients working by different mechanisms to provide the complete range of therapeutic and aesthetic benefits, including anticaries, antimicrobial, antigingivitis, antiplaque, anticalculus and anti-erosion, as well as anti-odor, mouth refreshment, stain removal, stain control and tooth whitening. In order for daily use oral care products, such as dentifrice and rinses to provide complete oral care it is often necessary to combine actives and additives, many of which have the disadvantage of causing negative aesthetics during use, in particular unpleasant taste and sensations and stain promotion. The unpleasant taste and mouth sensations have been described as having one or more of bitter, metallic, astringent, salty, numbing, stinging, burning, or prickling, and even irritating aspects. Typical ingredients for oral care use that are associated with these aesthetic negatives include antimicrobial agents such as cetyl pyridinium chloride, chlorhexidine, stannous and zinc salts; tooth bleaching agents such as peroxides; antitartar agents such as pyrophosphate, tripolyphosphate and hexametaphosphate; and excipients such as baking soda and surfactants. To mitigate the aesthetic negatives from these ingredients, oral care products are typically formulated with flavoring agents, sweeteners and coolants to taste as good as possible and provide a pleasant experience. In particular, it is desirable for oral care products to provide a refreshing cooling sensation during and after use. In addition to mitigation of negative sensations, sensate molecules are formulated into oral care compositions to convey a signal of efficacy. Such signals of efficacy include cooling, tingling, numbing, warming, sweetness, and rheological sensations such as phase change and fizzing or bubbling.
A large number of coolant compounds of natural or synthetic origin have been described. The most well-known compound is menthol, particularly 1-menthol, which is found naturally in peppermint oil, notably of Mentha arvensis L and Mentha viridis L. Of the menthol isomers, the 1-isomer occurs most widely in nature, and is typically what is referred by the name menthol having coolant properties. L-menthol has the characteristic peppermint odor, has a clean fresh taste and exerts a cooling sensation when applied to the skin and mucosal surfaces. Other isomers of menthol (neomenthol, isomenthol and neoisomenthol) have somewhat similar, but not identical odor and taste, i.e., some having disagreeable notes described as earthy, camphor, musty. The principal difference among the isomers is in their cooling potency. L-menthol provides the most potent cooling, i.e., having the lowest cooling threshold of about 800 ppb, i.e., the concentration where the cooling effect could be clearly recognized. At this level, there is no cooling effect for the other isomers. For example, d-neomenthol is reported to have a cooling threshold of about 25,000 ppb and 1-neomenthol about 3,000 ppb. (R. Emberger and R. Hopp, “Synthesis and Sensory Characterization of Menthol Enantiomers and Their Derivatives for the Use in Nature Identical Peppermint Oils,” Specialty Chemicals (1987), 7(3), 193-201). This study demonstrated the outstanding sensory properties of 1-menthol in terms of cooling and freshness and the influence of stereochemistry on the activity of these molecules.
Among synthetic coolants, many are derivatives of or are structurally related to menthol, i.e., containing the cyclohexane moiety, and derivatized with functional groups including carboxamide, ketal, ester, ether and alcohol. Examples include the ρ-menthanecarboxamide compounds, such as N-ethyl-ρ-menthan-3-carboxamide, known commercially as “WS-3”, and others in the series, such as WS-5 (N-ethoxycarbonylmethyl-ρ-menthan-3-carboxamide), WS-12 [N-(4-methoxyphenyl)-ρ-menthan-3-carboxamide] and WS-14 (N-tert-butyl-ρ-menthan-3-carboxamide). Examples of menthane carboxy esters include WS-4 and WS-30. An example of a synthetic carboxamide coolant that is structurally unrelated to menthol is N,2,3-trimethyl-2-isopropylbutanamide, known as “WS-23”. Additional examples of synthetic coolants include alcohol derivatives such as 3-(1-menthoxy)-propane-1,2-diol known as TK-10, isopulegol (under the tradename Coolact P) and ρ-menthane-3,8-diol (under the tradename Coolact 38D); menthone glycerol acetal known as MGA; menthyl esters such as menthyl acetate, menthyl acetoacetate, menthyl lactate known as Frescolat® supplied by Haarmann and Reimer, and monomenthyl succinate under the tradename Physcool from V. Mane. TK-10 is described in U.S. Pat. No. 4,459,425. Other alcohol and ether derivatives of menthol are described e.g., in GB 1,315,626 and in U.S. Pat. Nos. 4,029,759; 5,608,119; and 6,956,139. WS-3 and other carboxamide cooling agents are described for example in U.S. Pat. Nos. 4,136,163; 4,150,052; 4,153,679; 4,157,384; 4,178,459 and 4,230,688. Additional N-substituted ρ-menthane carboxamides are described in WO 2005/049553A1 including N-(4-cyanomethylphenyl)-ρ-menthanecarboxamide, N-(4-sulfamoylphenyl)-ρ-menthanecarboxamide, N-(4-cyanophenyl)-ρ-menthanecarboxamide, N-(4-acetylphenyl)-ρ-menthanecarboxamide, N-(4-hydroxymethylphenyl)-ρ-menthanecarboxamide and N-(3-hydroxy-4-methoxyphenyl)-ρ-menthanecarboxamide. Other N-substituted ρ-menthane carboxamides include amino acid derivatives such as those disclosed in WO 2006/103401 and in U.S. Pat. Nos. 4,136,163; 4,178,459 and 7,189,760 such as N-((5-methyl-2-(1-methylethyl)cyclohexyl)carbonyl)glycine ethyl ester and N-((5-methyl-2-(1-methylethyl)cyclohexyl)carbonyl)alanine ethyl ester. Menthyl esters including those of amino acids such as glycine and alanine are disclosed e.g., in EP 310 299 and in U.S. Pat. Nos. 3,111,127; 3,917,613; 3,991,178; 5,703,123; 5,725,865; 5,843,466; 6,365,215; 6,451,844; and 6,884,903. Ketal derivatives are described, e.g., in U.S. Pat. Nos. 5,266,592; 5,977,166 and 5,451,404. Additional agents that are structurally unrelated to menthol but have been reported to have a similar physiological cooling effect include alpha-keto enamine derivatives described in U.S. Pat. No. 6,592,884 including 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC), 5-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-MPC), and 2,5-dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone (DMPF); icilin (also known as AG-3-5, chemical name 1-[2-hydroxyphenyl]-4-[2-nitrophenyl]-1,2,3,6-tetrahydropyrimidine-2-one) described in Wei et al., J. Pharm. Pharmacol. (1983), 35:110-112. Reviews on the coolant activity of menthol and synthetic coolants include H. R. Watson, et al. J. Soc. Cosmet. Chem. (1978), 29, 185-200 and R. Eccles, J. Pharm. Pharmacol., (1994), 46, 618-630.
Structures built off of the cyclohexanecarboxamide backbone have been applied as anti-cancer agents as disclosed in WO 2009/067410. As shown in U.S. Pat. No. 4,150,052, only a select few of the cyclohexanecarboxamide derivatives had noticeable cooling. The molecules disclosed in WO 2009/067410 were evaluated for their TRPM8 activity in relation to the destruction of prostate cancer cells; however activating TRPM8 does not necessarily mean that a cooling sensation will be observed. Thus cooling would have been an undesirable effect and something they would have avoided.
The present invention provides methods for separating one or more compositions having coolant properties, wherein the cooling and refreshing sensation provided by the coolant(s) is optimized in terms of onset, intensity, or duration.